This invention is generally directed to a radio frequency (RF) local area network (LAN) which operates within a building and facilitates the sharing of the same frequencies utilized by existing microwave point-to-point systems.
The worldwide availability of additional frequencies for expanding communication demands is limited. The choice of frequency spectrum is further limited due to substantially different propagation characteristics at different frequencies. Therefore, different communication systems which need the same propagation characteristics all contend for desirable frequencies. This creates a need to share scarce RF channels wherever possible.
It is believed that the microwave frequency range of 2-20 gigahertz (GHz) represents a good choice for an in-building RF LAN. This choice is shaped by several factors. For such a system to be commercially viable, it must be reasonably cost effective. The ability to manufacture transmitters and receivers which can be sold at reasonable consumer prices suggests the range not exceed 20 GHz. At frequencies lower than about 2 GHz the size of components utilized in the RF portion of the system begin to increase in size such that the finished unit starts to become large. Also as the frequency decreases, the propagation characteristics becomes unfavorable for in-building communications where frequency reuse is desired since too great a communication range may occur. Another reason this choice of frequencies is desirable for such systems is that substantial contiguous bandwidths are available to support needed communication throughput.
The possibility of interference to an existing microwave point-to-point communications system by such an in-building RF LAN presents an important consideration. The present invention addresses this concern.